litres

Hi. I have been looking through the internet at ways in which to calculate the stocking of a aquarium, and different methods have given different sizes. For example one method says about a tank 185 liters while anothere method gives the answer of 300 liters. So the stocking that i was using is...

I keep reading people asking/commenting about filters and their litre per hour capabilities. how do you calculate/decide what filter is needed for what size tank ?  somebody was on about a 1500 l/p/h filter the other day and it got me wondering is all.   Cheers for any info